Method and apparatus with slips assembly for coupling tubulars without interruption of circulation

ABSTRACT

A slips assembly which comprises a plurality of slip segments which, when positioned adjacent to each other, form a collar, which collar is larger than the diameter of the tubular body of the tubular at the top of the drill string and smaller than the diameter the upset shoulder of the said tubular, there being a segment moving means which can move the segments together to from a collar slidably located around the body of the said tubular, which slips assemblies can also be utilised in conjunction with, or as part of, the couplers referred to in prior patent applications, either to support, raise or lower the string below, or restraint, lower or raise the tubular, or stand of tubulars, above.

This invention relates to drilling wells, and, more particularly tomethods and apparatus for drilling wells more efficiently and safely.

It is well known in the drilling industry, and particularly in the fieldof drilling for oil and gas, that drill strings comprise a largeplurality of tubular sections, drill pipes, joints of tubing, casing orconductors, hereinafter referred to as “tubulars”, which are connectedby male threads on the pins and female threads in the boxes. It is alsowell known that such tubulars must be added to the string of tubularsdown the hole, hereinafter referred to as the “string”, one by one or in“stands” of 2 or 3 already connected tubulars, as the string is loweredinto the hole drilled or being drilled. When it is necessary to withdrawthe string, in whole or in part, each tubular or stand of tubulars hasto be unscrewed one by one from the string as the string is raised tothe extent required.

Each time a new tubular is to be added to the string, the string israised and “slips” are placed around the topmost part of the string, afew feet below the top tool joint and these become wedged between thestring and the slips bowl when the string is lowered; the weight of thestring is thereby passed from the Top Drive to the slips. The slips arethereby “set” and grip the string enough to prevent the string fromdropping back into the hole.

This gripping relies on a combination of friction and indentation of thestring. Friction is generally not enough to prevent the string slippingand so the slips have metal inserts, which have a plurality ofprotrusions, which bite into the metal surface of the string. Although,designed to minimise damage to the surface of the string, inevitably thesurface suffers plastic deformation and repeated gripping causespermanent and increasing damage. Additionally, this area of the stringis located close to what is recognised as the high stress area, beingclose to the tool joint, which is necessarily more rigid. When thestring is required to bend, the transition area between the rigid tooljoint and the more flexible tubular shaft, or body, is a high stressarea This is the area that tends to fail first and any damage to thetubular surface makes such failures more likely.

Patent Applications PCT/GB/02815 and PCT/GB/03411, the contents of whichare hereby incorporated by reference, describe the making and breakingof tool joint connections under pressure inside a “Coupler”, so that mudcirculation can continue uninterrupted. When using such a Coupler, thereis a significant upward force on the tubular being added or removed dueto the internal mud pressure within the coupler. Hence, the tubular hasto be restrained from being forced upwards and out of the out theCoupler and for this purpose an ‘upside-down’ slips action is required,which can most conventionally be applied directly to the surface of thetubular shaft, or body. This too relies on gripping by indentation ofthe body surface; but at the other high stress area which is just abovethe tool joint.

The above patent applications, referred to, highlight the benefits ofusing the shoulder of the tool joint upset to resist axial movement ofthe string or tubular instead of relying on indentation of the bodysurface but the methods illustrated in those patent applications arecomplicated and occupy a relatively large amount of space

We have now devised an improved and simple method of actuating slipssegments to form a continuous slips collar around the tubular, to act onthe upset shoulder without damaging the tubular body.

According to the invention there is provided a slips assembly whichcomprises a plurality of slip segments which, when positioned adjacentto each other, form a collar, which collar is larger than the diameterof the tubular body of the tubular at the top of the drill string andsmaller than the diameter the upset shoulder of the said tubular, therebeing a segment moving means which can move the segments together toform a collar which can be slidably located around the body of the saidtubular.

In use the segments are moved together to form a continuous but loosecollar around the string or tubular and can then be slid up, or down, toengage the shoulder of the tool joint upset.

Concerning, first, the application of this invention to the supportingof the string; the slips are located in the slips body, which is acontinuous ring, supported on bearing mounted on the rig floor, rotarytable or even the BOP stack, used in conventional drilling equipment.

Preferably the slips segments are connected to the slips body by asliding keyway and are also connected to the slips base, which is acontinuous collar, encircling the box that serves the important purposeof ensuring that all the slips segments move in and out equally,preferably by a sliding keyway. Thus in use when the slips base is movedaway from the slips body, the slips segments move outwards from the axisof the string until they are clear of the passage of the relevant tooljoints through the slips assembly.

A preferred arrangement of the actuation of the slips segments is thatthe slips segments are guided by key ways in the slips body and slipsbase, such that the slips segments are forced to follow a controlledpath and the slips base itself ensures that the slips segments cometogether to form a perfectly aligned collar around the tubular. Thekeyways are preferably loose and smooth but can have a surface treatmentto reduce friction.

The slips base can be actuated up and down by mechanical, electrical orhydraulic means.

The slips base may, for some applications be preferred to retract underthe force of a spring, such that hydraulic pressure is only exerted tomove the slips base away from the slips body. In this way the slipssegments can be extended to form a slips collar around the string and,as the string is withdrawn from the well, each tool joint forces theslips segments apart as it passes; the segments sliding together again,under spring action, after each tool joint has passed. In this way, anyhydraulic failure results in the slips segments extending and thereforebeing ‘fail safe’ in operation. However, it is preferred that theextension of the slips segments to form the slips collar, isparticularly forceful, since the string may not otherwise be centralisedwithin the slips assembly and the force required to centralise the body,may be considerable.

The slips segments are preferably located in a conical slips body whichtapers upwards and outwards so that downward force applied to thesegments by the upset shoulder will hold the slip segments together. Theslips segments are wedged between the upset shoulder and the conicalslips body such that the greater the force applied by the upsetshoulder, the greater the force holding the slips segments together.

Preferably the surface of the slips segments adjacent the tubular is atangle to the axis of the tubular, which angle is slightly less than theangle of the upset shoulder to the axis of the tubular so that downwardpressure on the segments, due to the weight of the drill string, isapplied by the top end of the upset shoulder. For example, could be upto 2 degrees less than the angle of the shoulder to the tubular axis, asis discussed later.

Despite the small angle of the shoulder to the tubular axis, which canbe as little as 15°, the high force exerted by the weight of the string,which can be several miles long, is transferred directly through theslips body and the slips bearing, to the slips carrier. The slipsassembly can rotate with the string. The slips carrier, however, can bestatic in all directions, as is most likely when supporting a drillstring, or it can be raised or lowered when handling a tubular or whenused inside a Coupler.

The faces in contact with the slips body are preferably at such anangular slope compared to that of the faces in contact with the upsetshoulder, that the slips segments are neither squeezed out by thecompressive forces at these two faces, nor do they become overly jammedbetween them. Such a slope is typically 1 in 6 when designingconventional slips. In conventional slips, each slips segment (typically3 in number) supports a number of inserts, each of which has a number ofprotrusions (typically 40). These slips segments cannot form acontinuous collar since they must continue to move inwards as theprotrusions penetrate the body.

The faces in contact with the shoulder and with the slips body aredesigned to spread the forces over the maximum areas available and totransmit the forces over the shortest path possible. Similarly the slipsbody is designed to transmit these forces over the shortest distance tothe bearing and thence to the rig and/or well structure.

A feature of this invention is that, unlike the conventional use ofslips acting on the body of the tubular, the slips segments apply theforce over the whole surface of the upset shoulder and it is notrequired that the slips segments rely either on friction or onpenetration of the metal surface of the shoulder. Thus no ‘marking’,plastic deformation or damage is inflicted on the tubular body.

A feature of this invention is that, if the axial force of the weight ofthe string or the pressure on the tubular is high enough to exceed theelastic deformation of the surface of the upset shoulder, the resultingplastic deformation takes place preferentially at the least stressedpart of the tool joint.

This slips assembly can also be used upside down to hold a tubulardownwards, when it is being pushed into, or ‘snubbed’, into a highpressure space, as is required when a tubular or stand of tubulars arebeing introduced into a well, or a coupler, which is already highpressure.

Whether applied to supporting a string or subbing a tubular, the slipscarrier can be moved axially, up and down, to enable slips segments tomove into contact with the upset shoulder and, subsequently to raise orlower the string, or the tubular, respectively.

An advantage of the systems of the present invention over conventionalslipping systems is that slipping on the upset shoulder is more positiveand reliable than relying on friction and surface penetration and istherefore safer. Additionally the present invention, in which the slipssegments described herein provide a method of achieving this concept,provides a technical solution which combines simplicity, compactness andpracticality and enables the prior patents referred to above to beapplied with better effect.

This invention combines prior art and new techniques in a simple andcompact slips assembly that can support the string and/or restrain thetubular, when making or breaking connections, with or without the use ofa Coupler.

The slips assembly of the present invention can be used with a couplerof the type described in Patent Applications PCT/GB97/02815 andPCT/GB99/03411 either outside and beneath or within the coupler.

In Patent Application PCT/GB97/02815 there is provided a coupler for usein continuous drilling in which a drill string is rotated from a topdrive rotating means and drilling fluid is circulated down the drillstring which coupler comprises a means to grip the drill string andmeans to grip and seal a tubular lowered from substantially above, andthe upper and lower sections of the coupler being inside a chamberseparated into an upper half and a lower half by a blind preventerwhich, in its closed position prevents escape of drilling fluid from thedrill stand, whereby when the blind preventer is opened the tubular andthe drill stand can be brought into contact and joined together. Theslips assembly of the present invention can be used in the upper orlower half of the chamber.

In Patent Application PCT/GB99/03411 there is provided a well headassembly which comprises a BOP stack above which there are positionedsequentially: (i) a lower annular preventer (ii) lower grips and slipsadapted to engage a downhole drill string (iii) a blind preventer (iv)upper grips and slips adapted to engage a tubular to be added to thedrill string and (v) an upper annular preventer and in which the uppergrips and slips are able to pass through the blind preventer when theblind preventer is in the open position.

The orientation of the well head assembly refers to the well headassembly when in position on a drill string.

The slips assembly of the present invention can be used with the upperand/or lower slips.

The invention is illustrated in the accompanying drawings in which:

FIG. 1 is a cross section of the slips assembly, supporting a string

FIG. 2 is a cross section of the slips assembly, supporting a string andused in conjunction with grips to apply torque.

FIG. 3 is a cross section of the slips assembly, used to hold a tubulardown and within a Coupler under internal pressure.

FIGS. 4 a and 4 b are a cross section of a Coupler, using slipsassemblies to restrain both the drill string and the tubular within aCoupler and used in conjunction with grips to apply torque.

Referring to FIG. 1, the top end of the string is shown, which consistsof the tool joint box 10 and the top of the uppermost tubular 11 in thestring. The shaft or body 12 of the string is of smaller diameter thanthat of the upset of the box 10. The transition between the body 12 andupset 13 is the shoulder 14, which is usually at 30° to the axis of thetubular but 15° is becoming popular.

The shape of the shoulder's root 15 is varies depending on themanufacturer. The outside diameter of the body 11 is a quoted nominalstandard and the diameter of the upset 13 is also specific. However theupset diameter reduces as the tool joint becomes worn. The area of body12 immediately adjacent to the box 10 does not wear significantly but isoften of larger diameter than the quoted nominal standard OD of thetubular 11, depending again on the manufacturer.

Referring to FIG. 1, this invention essentially involves a slipsassembly 20 in which two or more slips segments 21 come together to forma continuous collar around the body 12 without gripping the body 12.

The string is lowered until the shoulder 14 of the box 10 contacts theslip segments 21, at which time the weight of the string is supported bythe slips segments 21, which are themselves wedged within the slips body22, which is a continuous ring, supported on bearing 23, mounted on therig floor, rotary table or even the BOP stack, 24, which areconventional drilling equipments.

The innovative aspects of this invention are the actuation of the slipssegments 21 and the configuration of the slips segments 21 as follows;

Concerning the actuation, the slips segments 21 are connected to theslips body 22 by a sliding keyway 28 and are also connected to the slipsbase 25 by a sliding keyway 27. Thus when the slips base 25 is movedaway from the slips body 22, the slips segments 21 move outwards fromthe axis of the string until they are clear of the passage of therelevant tool joints through the slips assembly.

The slips base 25 is actuated up and down by shaft 26 which can bemechanical, electrical or hydraulic. The hydraulic method shown requirespressure seals at 29 & 30 and is powered by hydraulic fluid passing viapassages 31 & 32 and the slip-rings at 33. A small bearing 34 is shownto complement the main bearing 23.

The slips base 25 may, for some applications be preferred to retractunder the force of a spring, such that hydraulic pressure is onlyexerted to extend it. In this way the slips segments 21 can be extendedto form a slips collar around the string and as the sting is withdrawnfrom the well, each tool joint forces the slips segments apart as itpasses; the segments sliding together again under spring action aftereach tool joint has passed. However, it is preferred that the extensionof the slips segments 21 to form the slips collar, is particularlyforceful, since the string may not otherwise be centralised within theslips assembly 20 and the force to centralise the body 11 may beconsiderable.

Concerning the configuration of the slips segments 21, the faces incontact with the upset shoulder 14 are designed to be the same angle ofslope as that of the shoulder 14, less a fraction of a degree to ensurethat any plastic deformation of the shoulder takes place preferentiallynear the peak 16, rather than near the root 15, which is a relativelyhigh stress area compared with the peak 16. Additionally, theseparticular faces of the slips segments 21 are cut back near the root 15to avoid contact with the variously shaped surface at the root 15.

The faces in contact with the slips body 22 are at such an angular slopecompared to that of the faces in contact with the shoulder 14, that theslips segments are neither squeezed out by the compressive forces atthese two faces, nor do they become overly jammed between them. Such aslope is typically 1 in 6 when designing conventional slips. (Inconventional slips, each slips segment (typically 3 in number) supportsa number of inserts, each of which has a number of protrusions(typically 40). These slips segments cannot form a continuous collarsince they must continue to move inwards as the protrusions penetratethe body.)

The faces in contact with the shoulder 14 and with the slips body 22 aredesigned to spread the forces over the maximum areas available and totransmit the forces over the shortest path possible. Similarly the slipsbody 22 is designed to transmit these forces over the shortest distanceto the bearing 23 and thence to the rig and/or well structure.

The keyways 27 & 28 are designed to be loose and smooth but may requiresurface treatment to reduce friction.

The slips base 25 is a continuous collar, encircling the box 10, thatserves the important purpose of ensuring that all the slips segments 21move in and out equally.

The vertical surface 17 serves only to force the body 12 into the centreline of the slips assembly 20, as the slips segments 21 move inwards toform the collar.

FIG. 2 shows the preferred relationship between the grips and slipsassemblies 40 & 20 in an application of the invention, wherein theconventional slipping and gripping of the body is replaced by slippingon the shoulder and gripping of the upset. The grips 42 act on the upset13 in the optimum area well clear of the hard banding area 18 and theweaker extremity of the box 19.

The gripping assembly 40 which is connected 41 to the slips assembly 20,can be driven mechanically, electrically or hydraulically. The drivesare shown as a pair of hypoid gear wheels 48 for illustrative purposes.The grips 42 can be actuated hydraulically via passages 44 & 45, throughadditional slip-ring seals 46 & 47.

This slips & grips assembly 40 & 20, can be positioned some 3 ft proudof the rig floor, above the conventional rotary table in order tooperate tongs above it at a convenient and ergonomic height.

FIG. 3 shows the upside down application of the slips assembly 60 whenrestraining a tubular 50 from being forced out of a pressure hull 51under high internal pressure. The bottom section of the tubular 50 isshown, comprising the tool joint pin 52, pin upset 53, upset shoulder 54and tubular body 55.

All key aspects listed for the slips assembly of FIG. 1 apply to FIG. 3.

Additionally, there is a slips carrier 61, which can be moved verticallywithin the pressure hull 51, by axial movement of 2 or more shafts 62,through which the hydraulic supplies 63 to actuate the slips actuationcylinders 64 can pass.

The whole slips assembly 60 can thereby be lowered to pass the pin 52down through the blind ram or valve 56 of a Coupler. The necessarygripping of the pin upset 53 when the tool joint connection is to bebroken is shown in FIGS. 4 a and 4 b.

The configuration shown is the most compact way known of containing aslips assembly within a diameter of some 18¾″ within a pressure hullcapable of passing tool joints of up to 9 inches in diameter. Suchpressure hull 51 typically being capable of operating at 5,000 psi.

FIGS. 4 a and 4 b shows the application of this innovative slipsassembly in conjunction with two sets of grips, within a Coupler aspreviously described in the patent applications referred to above asfollows:

The slips assembly 60 serves to restrain the tubular 50 from beingforced upwards and out of the high pressure space 70 within the pressurehull 71 of the Coupler 72.

This slips assembly 60 can be moved downwards so that the pin 52 entersand can be screwed into the box 10 and the of the topmost tubular of thestring 12

The bearings, allowing the slips assembly 20 and grips assembly 40 torotate are located below 73 and above 74.

The features of this invention, when applied to the Couplers describedin the referenced patents, are the compact method of actuation, whichenables the pressure hull to be minimised in size and weight and theshape of the slips segments, which enable force to be applied to theupset shoulder in the most efficient and safe manner, both of the stringand of the tubular.

1-32. Cancelled
 33. A slips assembly for preventing axial movement of atubular including a tool joint box having a shoulder comprising: (a) aplurality of slips segments arranged about said tubular and axiallypositioned to engage said shoulder; and (b) means for moving said slipssegments to engage said shoulder as a continuous collar.
 34. The slipsassembly of claim 33 in combination with a coupler having a pressurehull, a pair of first and second grips and a valve partition whereinsaid slips assembly is positioned between said valve partition and oneof said first and second grips.
 35. A method of securing a tubular witha plurality of surrounding slips segments, such tubular including ajoint box having a shoulder comprising: (a) moving said surroundingslips segments toward said tubular; (b) positioning said tubular andsaid slips segments so as to be in axial alignment with said shoulder;and (c) moving said slips segments toward said shoulder and engagingsaid shoulder to secure said tubular.
 36. The method of claim 34 whereinsaid slips segments are moved such as to not engage non-shoulderportions of said tubular.
 37. The method of claim 34 wherein said slipssegments are moved toward said shoulder such as to form a continuouscollar.
 38. A slips assembly for use with a drill string comprisingtubulars which slips assembly comprises a slips base and a slips bodyand in which there are a plurality of slip segments which, whenpositioned adjacent to each other, form a collar, which collar is largerthan the diameter of the tubular body of the tubular body of the tubularat the top of the drill string and smaller than the diameter of theupset shoulder of the said tubular, there being a segment moving meanswhich can move the segments together to form a collar which can beslidably located around the body of the said tubular.
 39. A slipsassembly as claimed in claim 38 in which the slip segments are locatedin a conical slips body so that downward force applied to the segmentsby the upset shoulder will hold the slip segments together.
 40. A slipsassembly as claimed in claim 38 in which the surface of the slipssegments adjacent to the tubular is at angle to the axis of the saidtubular which angle is less than the angle of the upset shoulder so thatdownward pressure on the segments due to the weight of the drill stringis applied by the top end of the upset shoulder.
 41. A slips assembly asclaimed in claim 40, in which the said surface of the slips segments isat an angle to the tubular axis of less than 2 degrees less than thesaid angle of the shoulder to the tubular axis.
 42. A slips assembly asclaimed in claim 38 in which the segments are slidably mounted in keyways, which key ways constrain the segments to move in a controlled pathto form the collar and align it around the said tubular.
 43. A slipsassembly as claimed in claim 42 in which the slips segments areconnected to the slips base so that all the slips segments move in andout equally on the sliding keyway.
 44. A slips assembly as claimed inclaim 38 in which the slips segments are located in a slips body whichis supported on a bearing mounted on the rig floor, rotary table or BOP(blow out preventer) stack.
 45. A slips assembly as claimed in claim 38in which there are three segments.
 46. A slips assembly as claimed inclaim 38 in which the slips base can be actuated up and down bymechanical, electrical or hydraulic means.
 47. A slips assembly asclaimed in claim 45 in which there is a spring positioned so that theslips base retracts under the force of a spring, such that mechanical,electrical or hydraulic pressure is only exerted to extend it.
 48. Aslips assembly as claimed in claim 38 in which the slips is able torotate with the string.
 49. A slips assembly as claimed in claim 48 inwhich the slips carrier is static in all directions.
 50. A slipsassembly as claimed in claim 38 in which, in use, the slips segmentsapply the force over the whole surface of the upset shoulder.
 51. Aslips assembly as claimed in claim 38 in which the slips are mounted ina slips carrier which slips carrier can be moved up and down in order tomove the top of the string towards or away from the tubular, or stand oftubulars, to, or from, which it is to be connected or disconnected. 52.A slips assembly as claimed in claim 38 which operates outside andbeneath a coupler for use in continuous drilling in which a drill stringis rotated from a top drive rotating means and drilling fluid iscirculated down the drill string which coupler comprises a means to gripthe drill string and means to grip and seal a tubular lowered fromsubstantially above, and the upper and lower sections of the couplerbeing inside a chamber separated into an upper half and a lower half bya blind preventer which, in its closed position prevents escape ofdrilling fluid from the drill stand, whereby when the blind preventer isopened the tubular and the drill stand can be brought into contact andjoined together, so that mud circulation can continue uninterrupted. 53.A slips assembly as claimed in claim 38 which operates inside the lowerchamber of a coupler for use in continuous drilling in which a drillstring is rotated from a top drive rotating means and drilling fluid iscirculated down the drill string which coupler comprises a means to gripthe drill string and means to grip and seal a tubular lowered fromsubstantially above, and the upper and lower sections of the couplerbeing inside a chamber separated into an upper half and a lower half bya blind preventer which, in its closed position prevents escape ofdrilling fluid from the drill stand, whereby when the blind preventer isopened the tubular and the drill stand can be brought into contact andjoined together so that mud circulation can continue uninterrupted. 54.A slips assembly, as claimed in claim 38 which operates inside the upperchamber a coupler for use in continuous drilling in which a drill stringis rotated from the top drive rotating means and drilling fluid iscirculated down the drill string which coupler comprises a means to gripthe drill string and means to grip and seal a tubular lowered fromsubstantially above, and the upper and lower sections of the couplerbeing inside a chamber separated into an upper half and a lower half bya blind preventer which, in its closed position prevents escape ofdrilling fluid from the drill stand, whereby when the blind preventer isopened the tubular and the drill stand can be brought into contact andjoined together, so that mud circulation can continue uninterrupted. 55.A slips assembly as claimed in claim 38 which is operated upside down toact upon the upset shoulder of a tubular, or the lowest tubular of astand of tubulars, when forcing or snubbing a tubular, or stand oftubulars, in a downwards direction, into a high pressure space.
 56. Aslips assembly, as claimed in claim 55, in which the slips are mountedin a slips carrier which slips carrier is moved up or down, in order tomove the tubular, or stand of tubulars, towards, and to connect with,the string, or away from, during a disconnection with the string.
 57. Aslips assembly as claimed in claim 55, in which the slips is inside theupper half of a coupler for use in continuous drilling in which a drillstring is rotated from a top drive rotating means and drilling fluid iscirculated down the drill string which coupler comprises a means to gripthe drill string and means to grip and seal a tubular lowered fromsubstantially above, and the upper and lower sections of the couplerbeing inside a chamber separated into an upper half and a lower half bya blind preventer which, in its closed position prevents escape ofdrilling fluid from the drill stand, whereby when the blind preventer isopened the tubular and the drill stand can be brought into contact andjoined together.
 58. A slips assembly as claimed in claim 55, in whichthe slips is inside the lower half of a coupler for use in continuousdrilling in which a drill string is rotated from a top drive rotatingmeans and drilling fluid is circulated down the drill string whichcoupler comprises a means to grip the drill string and means to grip andseal a tubular lowered from substantially above, and the upper and lowersections of the coupler being inside a chamber separated into an upperhalf and lower half by a blind preventer which, in its closed positionprevents escape of drilling fluid from the drill stand, whereby when theblind preventer is opened the tubular and the drill stand can be broughtinto contact and joined together.
 59. A slips assembly as claimed inclaim 55 in which the slips is outside and above the coupler for use incontinuous drilling in which a drill string is rotated from a top driverotating means and drilling fluid is circulated down the drill stringwhich coupler comprises a means to grip the drill string and means togrip and seal a tubular lowered from substantially above, and the upperand lower sections of the coupler being inside a chamber separated intoan upper half and a lower half by a blind preventer which, in its closedposition prevents escape of drilling fluid from the drill stand, wherebywhen the blind preventer is opened the tubular and the drill stand canbe brought into contact and joined together.
 60. A method for joining atubular to a drill string using a coupler which incorporates slips whichslips comprise a plurality of slip segments which, when positionedadjacent to each other, form a collar, which collar is larger than thediameter of the tubular body of the tubular at the top of the drillstring and smaller than the diameter the upset shoulder of the saidtubular, there being a segment moving means which can move the segmentstogether to form a collar slidably located around the body of the saidtubular method comprising lowering the string until the shoulder of thebox contacts the slips segments, at which time the weight of the stringis supported by the slips segments, which segments are on a slips basewedged within a slips body, which body comprises a continuous ring,supported on bearings, mounted on the rig floor, rotary table or the BOP(blow out preventer) stack, a tubular is then joined to the string, theslips base moved away from the slips body and the slips segments movedoutwards from the axis of the string until they are clear of the passageof the relevant tool joints through the slips assembly and the relevanttool joints passed through the drill segments.
 61. A method as claimedin claim 60 in which the surface of the slips segments adjacent thetubular is at angle to the axis of the said tubular which angle is lessthan the angle of the upset shoulder so that downward pressure on thesegments due to the weight of the drill string is applied by the top endof the upset shoulder.
 62. A method as claimed in claim 61 in which thedifference between the said angles is less than 2 degrees.
 63. A methodas claimed in claim 60 in which the segments are slidably mounted inkeyways and the segments are constrained by the keyways to move in andout equally on the sliding keyway in a controlled path to form thecollar and align it around the said tubular.
 64. A method as claimed inclaim 60 in which the slips base is actuated up and down by mechanical,electrical or hydraulic means.
 65. A method as claimed in claim 64 inwhich there is a spring positioned so that the slips base retracts underthe force of a spring, and mechanical, electrical or hydraulic pressureis only exerted to extend it.
 66. A method as claimed in claim 60 inwhich the slips assembly rotates with the string.
 67. A method asclaimed in claim 66 in which the slips carrier is static in alldirections.
 68. A method as claimed in claim 60 in which the slipssegments apply the force over the whole surface of the upset shoulder.69. A method as claimed in claim 60 in which if the axial force of theweight of the string or the pressure on the tubular is high enough toexceed the elastic deformation of the surface of the upset shoulder, theresulting plastic deformation takes place preferentially at the leaststressed part of the tool joint.